Electmcal connector



Feb. 21, 1956 2,735,997

K. E. PETERSON ELECTRICAL CONNECTOR Filed Oct 25, 1951 {JJJP I I n' INVENTOR.

A TTORNEYS.

. a... pr 2,735,997 7 ELECTRICAL CONNECTOR Kenneth E. Peterson, New Cumberland, Pa., assignor to Aircraft-Marine Products Inc., Harrisburg, Pa.

Application October 23, 1951, Serial No. 252,623

Claims. (Cl. 339-258) This invention relates to crimped electrical connectors and particularly to an electrical connector which can be crimped to produce a permanent, mechanically strong, corrosion-resistant electrically conductive connection between a terminal connector and an electrical conductor. The connection is of the known general type which is made by applying the ferrule portion of a connector over the bare end of a wire, or wires, either solid or stranded or a combination thereof, and permanently crimping the connector ferrule onto the conductor. The ferrule is crimped on the conductor so as to produce an intimate electrical contact between the ferrule and the conductor, the metals of the two parts being cold-forged and caused to flow together for this purpose.

Excellent connectors of this type are commercially.

available although room for improvement has remained. Thus, in particular, the type of crimp set forth in the Freedom Patent 2,535,013 gives an excellent connection, but its potentiality for crimping a wider range of wire sizes in a single size ferrule has not been fully realized with ferrules having serrations, e. g., as set forth in the Buchanan Patent No. 2,379,567 and in said Freedom patent. The fact that ferrules have been internally serrated assists in producing intimate electrical contact between the ferrule and the conductor by coining or coldfiow of the metals so as to break through any oxide film; and the serrations also contribute to a strong mechanical connection in that metal of one element is forced into the serrations in the other. Such connectors, however, have been subject to a tendency to crack when excessively stretched, and this has limited the range of wire sizes, requiring that the wire be engaged by the indented ferrule before the indentation extends to excessive depth.

Accordingly, it is a primary objective of my invention to provide an electrical connector which has the particular characteristic that it is not subject to mechanical failure, either in formation or in use, but which yet has the characteristic that it can be easily and economically made under mass production conditions, that it is highly conductive to electricity, highly resistant to atmospheric corrosion and is very durable and long lived. A further object is that in addition to the fact that the connector is not subject to mechanical failure, it will retain its superior qualities under torsional and tensile stress and that it may be formed with various types of metals, not only including copper, but aluminum, steel, bronze, etc. More particularly it is an object of this invention to provide a connector capable of being crimped by suitable indentors onto a wider range of wire sizes than has heretofore been recommended and which will permit the use of thinner metal ferrules than was feasible with connectors of the type disclosed in the Buchanan patent cited above and to achieve these objects Without sacrifice of mechanical or electrical security of connection.

The present invention contemplates that the interior of the ferrule shall be serrated, preferably with sharp rimmed troughs or indents with smoothly rounded bottoms. The invention, therefore, provides for the necessary and desired intimate electrical contact and mechanical bond between the ferrule and the conductor and yet' it does not subject the connector to mechanical failure by reason of tears started at the indentations i. e., due to' severe deforming of the metal over such indentations therein.

In this specification and the accompanying drawings I have shown and described a preferred embodiment of my invention and various modifications thereof; but it is tov be understood that these are not intended to be exhaustive nor limiting of the invention but, on the contrary, are given for purposes of illustration in order that others skilled in the art may fully understand the invention and the principles thereof and the manner of applying it in practical use so that they may modify and adapt it in various forms, each as may be best suited to the conditions of a particular use. a

In the accompanying drawings, in which the invention is specifically illustrated:

igure 1 is a perspective view of a connector embodying the invention showing internal indentations. Figure 2 is a fragmentary perspective view of a blank having V-trcugh serrations as heretofore used.

Figure 3 is a view similar to Figure 2 but showing thespherical indents.

Figure 4 is a perspective view of a blank for making a ferrule of the type of Figure 1.

Figure 5 is a perspective view of an electrical connector crimped on to the end of a multi-strand electrical cable.

Figure 6 is a sectional view taken transversely through the crimped connector ferrule of Figures 5 and 8 on line 66 of Figure 8.

Figure 7 is a plan view showing the connector and con-.

ductor of Figure 5 before crimping.

Figure 8 is a view similar to that of Figure 7 showing the parts after crimping. a

Figure 9 is a vertical section taken through a pair of crimping dies of another type with an electrical connector and a solid wire conductor positioned therebetween, the dies being in open position.

Figure 10 is a view similar to that of Figure 9 showing the dies partially closed.

Figure 11 is a view similar to that of Figure 9 showing the dies wholly closed.

Figurel shows an electrical connector generally in dicated at 20 combining a contact portion 22 anda ferrule portion 24. As shown the ferrule portion 24 is provided with indentations 21 of the dimple typeon its interior surface. Figure 2 shows by contrast sharp-bottomed groove type serrations on enlarged scale, Figure 3 being a fragment on the same. enlarged scale of material having dimple indentations 21 at the sectioned edges and showing also a staggered relation.

Figures 5, 7 and 8 show ferrule portion 24' telescoped over the stripped end 26 of an insulated conductor 28 and crimped onto the conductor by indents 30. These indents 30 as shown in these figures, are of a type covered by the Patent No. 2,535,013, and are side-by-side with rounded ends and bottoms spaced from the inner and outer transverse edges of ferrule portion 24. The indents as shown are located one on each side of a brazed seam 34.

In forming these indents the metal of the ferrule is drawn down with severe stretching and compression under the die and, especially in the end portions 32, with severe drag against the metal of the wire, which is increased by any serrations or indents which may be present in that area. The present invention avoids setting up lines of stress concentration which would facilitate tearing of the metal.

Figure 4 shows a ferrule blank before forming wherein U-type indents, i. e., smoothly rounded bottoms and Pa tented Feb. 21, 1956 sharply square rims 'are'utilized. The indents may be omitted fromthe area of greatest drawing of the metal (32 in Figure as more particularly described and claimed in application Serial No. 224,727, filed May 5, 1951 but it is an advantage of'the invention that that .is not necessary and orienting of the ferrule in the dies is avoided.

Figure 6 shows the crimped connection in cross section with the two longitudinal indents 30, the folded and extruded beads 36 along the edges of the indents and the lower nest portion 37. This figure also shows how the metal of the wire 26 is forged into a solid mass and into the indentations 21.0n the interior of the ferrule 24 to produceintimate electrical contact and a strong mechanical engagement with the ferrule 24.

In Figures 9, 10 and 11 there are shown upper and lower dies 39 and 40. The connector ferrule is shown at 24 with a solid wide 26a in place therein; and it will be observed that the die 39 has an indentor 42, and the lower die 40 is provided with an arcuate cavity 44, which retains the ferrule during indenting. The conductor as shown is at the smaller end of a range of sizes which may be used, and it may be of considerably larger diameter.

Figure 10 shows the ferrule 24 partly collapsed by the indentor 42, and it illustrates how the upper part of the ferrule 24 is deformed downward into contact with conductor 26a. The final configuration is shown in Figure 11 in which the connector ferrule has been compressed, extruded and drawn into the shape as shown while the wire is correspondingly deformed. The wall portions 35a in the inward sloping periphery of the indents have been thinned during the crimping operation. This thinning is due to extrusion of metals by pressure of the indentor 42 and to the deep drawing of the metal, especially at the ends corresponding to 32, which, as is well understood in the art of sheet metal working, tends to tear the metal if the dies are not very skillfully designed to distribute the drawing stresses. According to the present invention, however, there are no sharp bottomed serrations in the region of the ferrule where deep drawing occurs. The round bottom indents 21 avoid excessive weakening of the connector and their smooth dimple curvature, especially if the indents are arranged on equilateral triangles with the lines through adjacent indents oblique to the'tensile stress of drawing, avoids starting tears during extreme deforming under the indentor 42. Advantageously, any lines of indents in the region of deep drawing should be oriented parallel to the lines of tensile stress during the deep drawing.

In the manufacture of connectors in accordance with this invention the indents may be rolled or stamped or otherwise formed into a flat blank, as illustrated in Figure 4, after which the blank is rolled up to ferrule form and advantageously is brazed along seam 34, and annealed.

From the foregoing, it will be observed by those skilled in the art that my invention is well adapted to achieve the aims and objectives set forth above, and to economical manufacture.

The invention is well suited to common production methods and lends itself readily to a variety of modifications and adaptations.

I claim:

1. An electrical connector comprised of a ferrule portion adapted to be telescoped over and indented onto a bare electrical conductor, the interior of said ferrule portion being provided with smoothly round indents spaced apart and distributed in the areas of its inner face where the ferrule is to'be crimped, the bottom of each indent being farther radially from the central axis of said ferrule portion than adjacent areas of said inner face, whereby to provide a forged interlock and intimate electrical bond with the conductor when it is crimped thereon.

2. The structure of claim 1 wherein the indents are hemispherical dimples spaced apart.

3. The structure of claim 1 wherein the indents are hemispherical dimples spaced apart, and lines through adjacent indents being oblique to the length of the ferrule.

4. An electrical connector comprised of a tubular ferrule adapted to be telescoped over and indent-crimped onto a bare electrical connector, the interior of the ferrule having dimples in staggered relationship such that any lines through adjacent dimples are transverse to the lines of stress which may be imposed by drawing the indent during crimping, the bottom of each dimple being farther radially from the central axis of said ferrule than adjacent interior surfaces of said ferrule surrounding such dimple, whereby the mechanical failure of the ferrule will not be initiated by lines formed by said dimples.

5. An electrical connection comprising an electrical connector ferrule pressure-forged onto a conductor, said ferrule having inner face and said conductor having outer face, said inner face and said outer face being mutually contiguous, said inner face including a plurality of domelike indentations, said outer face including dome-like projections each the complement of an indentation with which it interfits, and said indentations being smoothly rounded so as to avoid concentrations of stress lines and disaligned so as to minimize danger of defining a tear line.

References Cited in the file of this patent UNITED STATES PATENTS 1,491,838 Zirnmermann Apr. 29, 1924 1,575,656 Stratford et a1. Mar. 9, 1926 1,833,145 Wilhelm Nov. 24, 1931 1,942,661 Paulus Jan. 9, 1934 2,109,837 Davis Mar. 1, 1938 2,379,567 Buchanan July 3, 1945 2,535,013 Freedom Dec. 19, 1950 2,604,508 Bergan July 22, 1952 

